What makes the difference in perovskite titanates?

Bussmann‐Holder, A.; Roleder, Krystian; Ko, Jae‐Hyeon

doi:10.1016/j.jpcs.2018.02.025

Cited by 15 publications

(13 citation statements)

References 105 publications

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“…The present conclusions are quantitatively consistent with phonon dynamics calculations [65] showing that the ground state of the RT phase is FE and F f f−p ∼ 1 − 2 meV per cubic cell. are much more different from experimental ones than those given by HSE.…”

Section: A Accuracy Of the Results And Free-energy Gain Of Fe Phasesupporting

confidence: 91%

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Watanabe

2019

Phys. Rev. B

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The properties of stress-free and biaxially strained stoichiometric SrTiO 3 in the absence and presence of antiferrodistortive (AFD) distortion were calculated ab initio. To obtain reliable results, multiple exchange correlation (XC) functionals, including the Heyd-Scuseria-Ernzerhof (HSE) hybrid functional, were used. HSE was the primary XC functional, while another functional provided a good lower bound of ferroelectricity (FE). The reliability of the calculations was further reinforced by the calculations of the strain and AFD dependence. In contrast with previous works, we show that the ferroelectric phase (C 1 4v , C 10 4v) is more stable in the absence of quantum and thermal fluctuations than the paraelectric phase (O 1 h , D 18 4h), even for the stress-free case, and clarify the properties of these FE phases. The energy gain of stress-free FE, in comparison with the thermal and quantum fluctuation energy, indicates that a paraelectric phase emerges at room temperature by thermal fluctuations, but is near 0 K marginally close to the FE phase, which aligns with the experimental incipient FE. This implies that the paraelectricity of stress-free SrTiO 3 in experiments contains incoherent atomic-scale FE regions. These results are consistent with the FE microregions (FMR), signatures of polar disorders, and the emergence of FE in SrTiO 3 due to impurities and defects. The value of spontaneous polarization P S could reach 10 μC/cm 2 in the absence of fluctuations, even for the stress-free case. In view of the earlier theory of the carrier layer at polar discontinuities, the present results may explain the conduction at the interfaces of the LaAlO 3 /SrTiO 3. In addition, an "enhancement of FE due to symmetry constriction" is proposed as an additional mechanism to the strain-enhanced FE in the epitaxial effect. For large compressive strain, e.g., 2%, the Perdew-Burke-Ernzerhof density functional for solids (PBEsol) yielded properties with P S > 20 μC/cm 2 , agreeing with HSE, and therefore is usable as a practical substitute of HSE for SrTiO 3 .

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Section: A Accuracy Of the Results And Free-energy Gain Of Fe Phasesupporting

confidence: 91%

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Watanabe

2019

Phys. Rev. B

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“…17,18 Recently, the phase above the Curie temperature T C received great interest in ABO 3 perovskites, both in ferroelectrics and antiferroelectrics, mainly because of the occurrence of polar regions (clusters) embedded in the nonpolar cubic lattice. 16,[19][20][21][22][23][24][25] These regions were also observed in PZO crystals doped with niobium Nb 5+ of different concentrations. 17,18 Foreign ions may play different roles, but the Nb 5+ in PZO lattice is specific in that it may create lattice defects because of its heterovalency.…”

Section: Introductionmentioning

confidence: 53%

“…Recently, the phase above the Curie temperature T C received great interest in ABO 3 perovskites, both in ferroelectrics and antiferroelectrics, mainly because of the occurrence of polar regions (clusters) embedded in the nonpolar cubic lattice . These regions were also observed in PZO crystals doped with niobium Nb 5+ of different concentrations .…”

Section: Introductionmentioning

confidence: 99%

Influence of Nb⁵⁺ ions on phase transitions and polar disorder above T_C in PbZrO₃ studied by Raman spectroscopy

Kajewski

Jankowska‐Sumara

et al. 2020

J Am Ceram Soc

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Micro‐Raman light scattering experiments on PbZrO3 (PZO) single crystal doped with Nb5+ have been investigated. Special attention was paid to the paraelectric (PE) phase in which nominally forbidden first‐order Raman spectra were detected at temperatures far above the phase transition TC. Complex Raman spectra were observed in the vicinity of three structural phase transitions. These results mainly from the coexistence of phases with different symmetries in a wide temperature range below TC. The Raman measurements have been compared with dielectric and optical observations and proved that polar nanoregions in a centrosymmetric lattice appear well above TC. It was shown that doping ABO3 perovskites with heterovalent ions like Nb5+ unbalances charge neutrality of the lattice and strongly extends the temperature range of polar regions. The investigations performed point out that in the PE matrix the interaction between electrons and lattice vibrations, as recently suggested for pure PZO, plays an important role.

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“…In spite of these extensive studies, the origin of precursor polarizations in the paraelectric phase is still not clearly understood. The universal scenario for the polar clusters based on the coupling between short-range structural instabilities and long-wavelength polar soft modes was proposed as an intrinsic effect [36,37]. First-principle calculations suggested the formation of eight minima along the <111> directions in the local free energy, which persist up to ( T C + 400) °C in the paraelectric phase [38].…”

Section: Introductionmentioning

confidence: 99%

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements

Lee

et al. 2018

Molecules

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The nature of precursor phenomena in the paraelectric phase of ferroelectrics is one of the main questions to be resolved from a fundamental point of view. Barium titanate (BaTiO3) is one of the most representative perovskite-structured ferroelectrics intensively studied until now. The pretransitional behavior of BaTiO3 single crystal grown using a solid-state crystal growth (SSCG) method was investigated for the first time and compared to previous results. There is no melting process in the SSCG method, thus the crystal grown using a SSCG method have inherent higher levels of impurity and defect concentrations, which is a good candidate for investigating the effect of crystal quality on the precursor phenomena. The acoustic, dielectric, and piezoelectric properties, as well as birefringence, of the SSCG-grown BaTiO3 were examined over a wide temperature range. Especially, the acoustic phonon behavior was investigated in terms of Brillouin spectroscopy, which is a complementary technique to Raman spectroscopy. The obtained precursor anomalies of the SSCG-grown BaTiO3 in the cubic phase were similar to those of other single crystals, in particular, of high-quality single crystal grown by top-seeded solution growth method. These results clearly indicate that the observed precursor phenomena are common and intrinsic effect irrespective of the crystal quality.

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What makes the difference in perovskite titanates?

Cited by 15 publications

References 105 publications

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Influence of Nb⁵⁺ ions on phase transitions and polar disorder above T_C in PbZrO₃ studied by Raman spectroscopy

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements

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What makes the difference in perovskite titanates?

Cited by 15 publications

References 105 publications

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Ferroelectricity of stress-free and strained pure SrTiO3 revealed by ab initio calculations with hybrid and density functionals

Influence of Nb5+ ions on phase transitions and polar disorder above TC in PbZrO3 studied by Raman spectroscopy

Precursor Phenomena of Barium Titanate Single Crystals Grown Using a Solid-State Single Crystal Growth Method Studied with Inelastic Brillouin Light Scattering and Birefringence Measurements

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Influence of Nb⁵⁺ ions on phase transitions and polar disorder above T_C in PbZrO₃ studied by Raman spectroscopy